To add to Matt's post...
InDesign was actually _started_ at Aldus as a major upgrade to PageMaker, so it _technically_ didn't kill PageMaker. The "InDesign" technology was the main reason Adobe bought the company in 1994.
InDesign needs a number of long-document upgrades to compete with FrameMaker, especially in the book area. However, the last time it got major long-document upgrades was back in 2007, so I wouldn't hold my breath! That said, I have created numerous 800-1000-page books in InDesign.
Of course, if you are using a structured workflow (XML, DITA), then there is no question that Frame is the one to use. (InDesign does have some basic XML features, but it can't compare to Frame.)
... View more